Armored reenforced-concrete slab



April 17, 1928. 1,666,15

J. A. VOSKAMP ARMORED REENFORCED CONCRETE SLAB Filed Oct. 25. 1926 2 Sheets-Sheet l Q Q W/EZEFZZK/U 4 Q BY ATTORNEY April 17, 1928.

J. A. VOSKAMP ARMORED REENFORCED CONCRETE SLAB Filed Oct. 25. 1926 2 Sheets-Sheet 2 INVENTOR ATTORNEY Patented r. 17, 1928.

UNITED STATES 1,666,156 PATENT orricsi JOHN A. VOSKAMP, OF NEW YORK, N. Y., ASSIGNOR T IRVING IRON WORKS COMPANY,

A CORPORATION OF NEW YORK.

ARMORED REENFORCED-GONCRETE SLAB.

Application filed October 25, 1926. Serial No. 143,808.

This invention embodies an improvement on that disclosed 'in U. S. Letters Patent No. 1,526,069, granted Walter E. Irving February 1925, and has for its object the imparting of greater strength per unit of weight to reenforced concrete slabs or plates of the character described in said patent, or effecting a saving in material and consequent weight while retaining a given degree of strength in such a structure.

The dominating feature of the invention is based on the discovery that a reenforced concrete slab extending between two spaced apart supports and having substantially parallel bars or strips embedded in its upper surface presents the greatest resistance to the bending force exerted by a'superimposed load when such bars or strips extend at right angles to the compression stresses created in the upper portion of such slab or plate by any downward deflection thereof, i. e. extend parallel to the edges of the sills or abutments between and across which such slab or plate is supported.

* As any downward deflection of such plate or slab produces tension stresses in its lower portion it is evident that the reenfo-rcing bars or strips in such lower portion should, however, extend across or at right angles to the supporting sills or abutments. Consequently the basic feature of the present invention is a reenforcing system for concrete slabs or plates comprising two sets of generally parallel reenforcing elements, one set being embedded in the 'upper portion and the other in the lower portion of the slab, the elements of one set extending crossways of the elements of the other set.

The best form of apparatus at present known to me embodying the above mentioned and other improvements, together with certain modifications, are illustrated in the accompanying two sheets of drawings, in which:

Fig. 1 is a diagrammatic plan view of a portion of a bridge showing a part of the reenforced flooring supported by sills running lengthwise of the bridge, parts being broken away.

i Fig. 2 is a diagrammatic detail of the same, on a larger scale.

I Fig. 3 is a side elevation with parts broken away.

Fig. 4 is a cross section on line 44 of 5 Fig. 2.

girders 12 which sustain the longitudinally extending floor sills 13. Upon these sills rests the reenforced concrete flooring comprising either a series of slabs, or continuous sheets of reenforced concrete extending entirely across the bridge except for the usual expansion joints occurring at proper distances. This reenforced concrete element comprises an upper metal grating preferably compose'd-of straight barsl with intervening bent spacing strips 3 usually riveted thereto, as shown at 5, 5; a lower metal grating composed of parallel straight bars 2, and intervening bent spacing strips 4 similarly fastened together; and the body of concrete 7 filling the space between said gratings and the mesh openings therein.

These upper and lower gratings may be spaced apart by vertically extending spac v ing strips 6 which may be conveniently fastened to the gratings by rivets 15 passing through holes 16 in the straight bars. While these spacing strips 6 are shown exactly vertical, of course they might be otherwise disposed in such manner as may best serve to withstand the shearing stresses created in the slab by superposed loads. As best shown in Fig. 1, the straight bars and all other longitudinals of the lower grating should extend crosswise of the sills while the longitudinals of the upper grating should extend in the direction of the traffic and crosswise to the bars of the lower grating.

By this arrangement I secure the eatest strength of slab in resisting the ownward deflection produced by a superposed load and also the greatest resistance to the punching shear action produced by' highly concentrated loads such as the wheels of very heavily loaded motor trucks. The straight bars 2 of the lower grating serve as tension members extending across from one sill to the other, resisting the tension tal Ill

stresses produced by an initial downward deflection of the slab. llhe upper portion of the slab at such time is subjected only to compression stresses, and l have found that if-the, upper grating is arranged as-shown, so as to have its longitudinals extending at right angles to such stresses, the concrete will withstand a greater compressive strain than when the upper grating bars 1, 1, extend parallel to said stresses. Apparently the reason for this is that if the latter, arrangement is employed the straight bars of the upper grating buckle slightly under very heavy stresses and free the grating elements from the masses of concrete in the meshes of said grating, thereby disintegrating the entire structureand eliminating all benefits which might otherwise result from the use of concrete. When a reentorced slab of this description is subjected to heavy bending stresses in a testing machine the masses of concrete in the mesh of the upper grating will sometimes crack away from the gratin so completely that they can all be picke out by hand. If, however, the arrangement shown in the drawing is employed, the bent spacing strips 3, 3. have a certain elasticity in the direction of the compression strains in the upper portion of the slab and the entire compression force is absorbed by the concrete, which by itself is capable of a somewhat greater resistance to compression than the straight bars 1. As a result, there is then no disintegration of the reenforced slab and it will withstand greater bending stresses than when so constructed as to have its upper longitudinals extending crosswise of the supporting sills.

Also it is otherwise advantageous to have the straight bars 1 of the upper grating extend lengthwise of the bridge. because the broad tired wheels and double wheels of very heavy trucks will then extend over and rest on a greater number of said straight bars and the concentrated load created by said truck wheels will be distributed by said bars over a greater area of the slab. While the area of contact between such a double truck wheel and the floor of the bridge may extend 14 or 15 inches in a direction crosswise of the bridge, it will not extend more than two or three inches in a direction lengthwise of the bridge because thehard rubber tires will not-flatten down into contact with the bridge floor over a space wider than that. Consequently if the straight bars 1 are spaced apart a distance of two and a half inches from center to center and extend crosswise of the-bridge, i. e. at right angles to the flow of traiiic, two of them will have -to support the entire downward thrust of a passing truck wheel. On the other hand, with the arrangement shown in the drawings, five or six of the longitudinally extending bars 1, 1, would come under each truck messes wheel and so distribute the load over a luch greater area of the slab. Also in the latter construction the thrust would be continuous along each bar as the wheel rolled over it thereby reducing the impact to'a minimum,

\ tain of the straight bars 2, 2 of the lower grating are extended upward by increasing their widthuntil they come in contact with the upper grating, and, in order to save weight, sections of the intermediate portions of such wide bars are punched out as shown at 10, 10. These extended skeleton bars 2 then serve as spacing elements between the gratings and they may be fastened to the upper grating in any convenient manner, as by the supporting hook 8 riveted to one of the upper bars 1.

If it is desired to lighten the structure still more, the spacing strips 4, 4, in the lower grating may be removed and the lower part of the reenforcing structure further skeletonized by substituting ordinary tension rods 2, 2*, for the lower grating, as shown in Fig. 7, said tension rods being supported by hooks 9 passing through hole 16 in the straight bars 1, 1, of the upper grating. lit desired, a few cross binding rods 14 may be loosely placed upon the tension rods 2" or upon the bars 2*, as shown in Figs. 6 and 7.

Many of the advantages of. my invention may also be preserved in thin slabs for use in forming light floorings, suitable for use in buildings and similar situations, by substituting for the upper and lower gratings previously described a heavy netting of diamond mesh embedded in the upper and lower portions of the concrete 7, the two sets of wire netting being arranged crosswiseone of the other as shown in'Fig. 8. In such case the greatest resistance to tension strains whichis presented lengthwise of the netting makes the lower netting 22 most etiicient as a tension reentorcement for the lower portion of the slab wire, while the upper netting 21, extending crosswise of the lower netting and of the compression strains in the upper portion of the slab, leaves the concrete free to exert its full strength in resisting such compression strains, and ,at the same time gives its toughening and wear-resisting effect to the upper surface of the slab.

For the sake of unformity and convenllll ascents ien'ce in manufacture it is advisable to have the distance from center line to center line of the straight bars 1, 1, and 2, 2, one half the di=tance between adjacent rivets 5, 5, and then, by punching the intermediate holes 16, 16 in all the straight bars halfway between the rivet holes, these free holes will come one over the other when the two gratings are placed crosswise one above the other and afford convenient means for as tening the vertical spacing members such as 6 and 9, or the hooks 8 which cooperate with the skeleton extension bars 2 as shown in Fig. 6. v 7

Among the advantages resulting from the use of the invention, in addition to those above pointed out, may be mentioned the armoring effect on the wearing surface ofthe roadway produced by the upper grating without reducing the resistance to compression stresses in that portion, of the plate, and the great saving in the cost of material for the main supporting structure of the bridge rendered possible by the great reduction in weight of the flooring slabs when my invention is used, the total dead load on the bridge being thereby greatly reduced.

Having described my invention 1 claim: 1. A reenforced concrete structure comprising, in combination, a plurality of parallel spaced-apart supporting sills and a reenforced concrete slab supported thereby, said slab having two reticular reenforcing members embedded therein and lying in substantially parallel planes, one, near the lower surface thereof, having tension members extending across said supporting sills and the other, near the upper surface thereof, arranged crosswise of the first mentioned reticular member.

2. A reenforced concrete slab adapted for use as a flooring and similar purposes, which comprises two substantially parallel metal gratings each composed of a series of relatively heavy parallel straight bars with intervening bent spacing strips of considerably lesser weight, the bars of one of said gratings extending substantially at right angles to those of the other, and a body of set concrete filling the space between said gratings and also the mesh spaces therein whereby when said slab is placed on spaced-apart supports on the ends of which the lower grating bars rest, all tension stresses will be parallel to said bars, while all compression stresses will be exerted crosswise of the bars of said upper grating.

3. A structure adapted to support heavy moving bodies, comprising. in combination,

a plurality of spaced-apart supporting sills extending in the direction along which said bodies are expected to move and a reenforced concrete slab supported thereon, said slab having twometal gratings embedded therein adjacent either surface thereof, each 6. A structure such ,as defined in claim 3 combined with spacing means between said gratings comprising skeleton upward extensions of certain of the straight bars of said lower grating.

7. A reenforced concrete structure adapted to support heavy moving loads comprising, in combination.- apart supporting sills extending in the direction along which said loads are expected to move, and a reentorced concrete slab sup- I ported thereon, said slab having two sets of metallic reenforced means embedded therein, one at the upper surface of said slab having members extending parallel to said a. plurality of spacedsills, and the other in the bottom half of said slab having members extending across said sills.

8. A structure such as defined in claim 7 combined with means holding said reenforcing members evenly spaced apart in all directions.

9. In a reenforced concrete slab or plate suitable for flooring or the like purposes the combination with two metallic gratings embedded therein, one near its upper surface and the other near its lower surface, the longitudinals of one grating being arranged substantially at right angles to the other.

grating of skeletonized. integral extensions of certain of the bars of one-of said gratings resulting from the employment of metal strips for said bars much wider than the depth of said grating, said strips having a considerable portion of their material punched out, which skeletonized extensions extend vertically sufliciently to touch the other grating when the parts are assembled and so serve as spacing members between said gratings; whereby an accurate spacing between said gratings can be ensured merely by proper designing of the elements of the completed structure in the process of manufacture thereof.

10. A structure such as defined in claim 9 combined with hooks fastened to said upper grating and engaging said skeletoniz'ed extensions from said lower grating.

11. A structure such as defined in claim 9 combined with hooks fastened to said upper.

grating and engaging said skeletonized extensions from said lower grating and tension rods extending through the openings in said skeletonized extensions.

12. As an element adapted for use in the building up of a reenforced concrete slab, the combination of a plurality of straight bars and means for holding, sa id bars evenly spaced apart laterally, certain of said straight bars being much wider than said spacing means and having their free" portions, which extend beyond said spacing means, cut away to form a skeleton adapted for usea-s a combined spacing strengthening and concrete holding means when associated with a second reticulated metal reenforcing means and embedded therewith in a body of concrete.

JOHN A. vosmnr. 

